The adaptability of the nervous system in response to changes in the environment is essential for the survival of an animal. With the exception of sensory nerves which can receive information about the environment directly, most nerve cells receive such information only indirectly through changes in their synaptic and humoral inputs. It is the ability of neurons to change in response to changes in these inputs which ultimately produces many of the behavioral and physiological adaptations necessary for survival. The proposed research deals with adaptive changes in synaptic neurochemistry in peripheral and central adrenergic neurons. The project has three immediate objectives: 1) To study the role of trans-synaptic activity in regulating the levels of the key enzymes in the synthesis of the neurotransmitter, norepinephrine, in peripheral adrenergic neurons by direct electrical stimulation of the neural input in vivo: 2) to investigate the mechanism of this trans-synaptic regulation using a variety of pharmacological agents under controlled in vitro conditions; 3) to initiate studies of the role of the pituitary-adrenal system in controlling neurons. These studies should help to elucidate the mechanisms involved both in the development of the adrenergic system and in its modification during adult life, particularly during periods of intense stress.